<body>
  <div id="el" style="width: 100px;height: 100px;background-color: lightblue;"></div>
  <div id="el2" style="width: 100px;height: 100px;background-color: red;"></div>
  <button id="pause-btn" >pause</button>
  <button id="resume-btn" >resume</button>
  <button id="reset-btn" >reset</button>
  <script type="module" src="./animation-demo.js"></script>
</body>